Frilled sharks a creature straight out of legend
Frilled sharks (Chlamydoselachus anguineus) live in the pitch black environment of the deep sea, an environment that is considered one of the most extreme environments on the planet and its little wonder why with pressures reaching up to 1000 times our normal atmospheric pressure and temperatures that really get above 4°C unless you go to a hydrothermal vent, the lack of light meaning that the only form of primary production is via chemosynthesis at hydrothermal vents making food incredibly scarce. The deep sea is such a inhospitable place to live that in the 19th century scientists believed that nothing could live deeper than 300 fathoms. This was later disproved and there has now been over 15,000 deep sea species described.
A legend comes to life
Frilled shark carcass washing up on shore are thought to be partially behind the legends of sea serpents and it would be hard to blame any person that found one wish the frilled sharks slender eel like appearance and its maximum size of 2m. They also have a mouth that contains roughly 300 teeth that have three prongs (tricuspid), they also have six gill slits which is one extra than most species of sharks
has as well as having gills that extend out of its gill slits.
All of these things and more adapt it perfectly for its deep sea environment. Its many tricuspid teeth allow it to ensnare any prey it manages to catch, while its extended gills allow it to maximize its gill area for oxygen absorption in an environment that is has low oxygen levels. Frilled sharks also have a liver filled with a substance called squalene that’s density is low enough that it floats in water, all sharks have this but frilled sharks have a huge liver so that they don’t have to expend energy keep its buoyancy, this paired up with the slow metabolism that is found in most deep sea species makes the frilled shark incredibly well suited to living in a environment where food is scarce and their next meal may not come for some time. Frilled sharks are so well adapted to their environment that they have remained largely unchanged for many thousands of years and thus share some features only found in ancient long extinct sharks, one such feature is the frilled sharks open lateral line, the lateral line is a sensory organ that runs the side of a sharks body that is used to sense movement and changes is water pressure, most sharks have skin covering their lateral line where as frilled sharks do not this means that they are ultrasensitive to movements and changes of pressure around their body.
Frilled sharks have a very wide spread but erratic distribution in the Atlantic and Pacific Ocean. They are
normally found living at depths between 50-200m but has been found as deep as 1,570m although its thought that it normally will only dive to 1,200m at its deepest. The first frilled sharks were found by scientists in Suruga Bay in Japan in the 1880’s.
Life of a monster
Life in the deep ocean is hard, finding food is a challenge in its self let alone catching it. Due to this plus the fact that the majority of frilled shark specimens that have been found have had empty stomachs it is thought that frilled sharks are able to swallow larger prey whole like a snake by extending their jaws and stomachs. From the frilled sharks found with their stomach contents present it is thought that they predate mainly on fish and squid although it is unsure if the frilled shark has the capabilities to actively hunt prey that can move at such a rapid pace or if they pick of weakened prey or act like ambush hunters.
Frilled sharks have one of the longest gestation periods of any shark with a time of 3.5 years. They embryos grow inside eggs in the mother and receive nutrients from the mother. Unlike most sharks frilled shark mothers only use their right uterus for embryodevelopment whereas most use both left and right.
The frilled sharks long gestation time, slow growth rate and small litter size means they have the potential to be one of the most vulnerable species for over exploitation, unusually it is very really caught and isn’t targeted by any fisheries so has been given the rating of ‘least concern’ by the IUCN. This may change in the future as investigations into the exploitation of deep sea resources may start to happen bringing this shark into more direct contact with humans.